137 



BLOOD PRESSURES IN MAN, NORMAL AND PATHOLOGICAL 329 



3. Pressure required to cause stasis of corpuscular flow under the 

 microscope — by Danzer and Hooker's (35) micro-capillary tonometer, 

 a different criterion from those used in the preceding methods. They 

 found values of 18 to 26.5 mm. Hg averaging 22 mm. Boas and 

 Frant (17) using the same method reported normal capillary pressures 

 at 18 to 22 mm. Hg, rarely above 30 mm. ; high pressure cases reading 

 usually between 30 to 60 mm. In essential hypertonus capillary pres- 

 sure was found to be normal, i.e., below 30 mm. Boas and Mufson 

 (18) found a much higher mortality in a high capillary pressure group 

 (5 deaths in 28). Their post-mortem findings (a small number of 

 cases) did not support Kylin's hypothesis of an association of high 

 capillary pressure with glomerular nephritis. 



4. Piercing capillaries with a very fine capillary glass needle (con- 

 taining saline at a measured pressure) under the microscope to measure 

 the pressure in a capillary loop — by Carrier and Rehberg (26). The 

 values 45 to 75 mm. H2O in two subjects at 7 cm. below the clavicle — 

 reported by this method — unfortunately unsuited for clinical applica- 

 tion — are relatively low and lend support to L. Hill's repeatedly stated 

 view as to the lowness of capillary pressure. The venous pressure was 

 parallel to the capillary pressure. 



Supposing that the pressure in the minute vessels of the skin can be 

 accurately measured, there remains the question of the application of 

 such results to the conditions of the general circulation. Pressures in 

 the finger and hand are naturally influenced profoundly by the local 

 conditions of arterial tone as affected by vasomotor influences, heat, 

 cold, exercise, sleep, etc., with the result that the digital pressure may 

 rise while the brachial pressure falls, or vice versa. It is hardly neces- 

 sary to recall the frequently opposed conditions in the skin and splanch- 

 nic areas, as with muscular exercise, asphyxia, adrenalin, etc., also 

 the different incidence of the vaso-dilator effects of acetyl-choline — 

 as described by Reid Hunt (69) — marked in the skin, slight in the liver 

 and intestine, very slight in the voluntary muscles. Again the strong 

 constriction of the renal vessels, which is presumably the cause of the 

 anuria known to occur during short spells of violent muscular exercise, 

 is associated with increased pressure in the skin. The habitually cold 

 or habitually warm hands of different persons, naturally involve wide 

 variations in the pressure relations of the minute cutaneous vessels. 



There are thus no means of ascertaining the relations between pres- 

 sure measurements in the skin and the pressures existing in other 

 parts, internal organs, etc., and how they stand with regard to the 



